Paramecium exhibits an avoidance response to mechanical, chemical and electrical stimulation in which the organism reverses its direction of movement by reversing the motion of its cilia. Hundreds of mutant lines with altered locomotory behaviors are available. The surface membrane surrounding cilia control ciliary activity and the defects in many Paramecium behavioral mutants involved altered surface membrane excitation. Defects in membrane excitation in some strains are known to have altered Ca 2 ion or K ions grating/channel mechanisms. Other mutants may have defective ion pumps. The goals of this proposal are to identify altered structural components and to determine the function of the normal components and the structural changes that led to loss of different functions in different mutants. We will screen mutants representing as many different genetic loci and phenotypes as possible. The methods we will use to identify the structural alterations include immunological and affinity column techniques and polyacrylamide gel isoelectric focusing and electrophoretic methods. To determine the specific function of different proteins identified as altered in different mutants, we will, for example, prepare antibodies of a purified protein, determine its subcellular location and use antibodies to interfere with normal protein function. The criteria for interference with normal function will include changes in ion fluxes and locomotory behavior. Specific binding of ca ion to the membrane will also be measured on the assumption that in at least some of the mutants Ca2 ion binding capacities will be defective. By using a variety of paramecia mutants, we hope to dissect out various structural components involved in the complex process of membrane excitation. The P. aurelia and mutants system is a suitable model for the more complex excitable membranes of nerves and muscles which exhibit voltage-dependent channels and gates.